Treatment with calcimimetics in kidney transplantation

Post-Transplant Bone Disease in Kidney Transplant Recipients: Diagnosis and Management

Kidney transplantation is the preferred gold standard modality of treatment for kidney failure. Bone disease after kidney transplantation is highly prevalent in patients living with a kidney transplant and is associated with high rates of hip fractures. Fractures are associated with increased healthcare costs, morbidity and mortality. Post-transplant bone disease (PTBD) includes renal osteodystrophy, osteoporosis, osteonecrosis and bone fractures. PTBD is complex as it encompasses pre-existing chronic kidney disease-mineral bone disease and compounding factors after transplantation, including the use of immunosuppression and the development of de novo bone disease. After transplantation, the persistence of secondary and tertiary hyperparathyroidism, renal osteodystrophy, relative vitamin D deficiency and high levels of fibroblast growth factor-23 contribute to post-transplant bone disease. Risk assessment includes identifying both general risk factors and kidney-specific risk factors. Diagnosis is complex as the gold standard bone biopsy with double-tetracycline labelling to diagnose the PTBD subtype is not always readily available. Therefore, alternative diagnostic tools may be used to aid its diagnosis. Both non-pharmacological and pharmacological therapy can be employed to treat PTBD. In this review, we will discuss pathophysiology, risk assessment, diagnosis and management strategies to manage PTBD after kidney transplantation.

Management of Post-transplant Hyperparathyroidism and Bone Disease

Significant advances in immunosuppressive therapies have been made in renal transplantation, leading to increased allograft and patient survival. Despite improvement in overall patient survival, patients continue to require management of persistent post-transplant hyperparathyroidism. Medications that treat persistent hyperparathyroidism include vitamin D, vitamin D analogues, and calcimimetics. Medication side effects such as hypocalcemia or hypercalcemia, and adynamic bone disease, may lead to a decrease in the drugs. When medical management fails to control persistent post-transplant hyperparathyroidism, treatment is a parathyroidectomy. Surgical techniques are not uniform between centers and surgeons. Undergoing the surgery may include a subtotal technique or a technique including total parathyroid gland resection with partial heterotopic gland reimplantation. In addition, there are possible post-surgical complications. The ideal treatment for persistent post-transplant hyperparathyroidism is the treatment and prevention of the condition while patients are being managed for their late-stage chronic kidney disease and end-stage renal disease.

Electrolyte and Acid-Base Disorders in the Renal Transplant Recipient

Kidney transplantation is the current treatment of choice for patients with end-stage renal disease. Innovations in transplantation and immunosuppression regimens have greatly improved the renal allograft survival. Based on recently published data from the Scientific Registry of Transplant recipients, prevalence of kidney transplants is steadily rising in the United States. Over 210,000 kidney transplant recipients were alive with a functioning graft in mid-2016, which is nearly twice as many as in 2005. While successful renal transplantation corrects most of the electrolyte and mineral abnormalities seen in advanced renal failure, the abnormalities seen in the post-transplant period are surprisingly different from those seen in chronic kidney disease. Multiple factors contribute to the high prevalence of these abnormalities that include level of allograft function, use of immunosuppressive medications and metabolic changes in the post-transplant period. Electrolyte disturbances are common in patients after renal transplantation, and several studies have tried to determine the clinical significance of these disturbances. In this manuscript we review the key aspects of the most commonly found post-transplant electrolyte abnormalities. We focus on their epidemiology, pathophysiology, clinical manifestations, and available treatment approaches.

Timing of parathyroidectomy in kidney transplant candidates with secondary hyperparathryroidism: effect of pretransplant versus early or late post-transplant parathyroidectomy

BACKGROUND

The timing of parathyroidectomy in kidney transplant candidates suffering from secondary hyperparathyroidism before versus early or late after transplantation remains controversial.

METHODS

The short-term follow-up cohort comprised 66 patients with 1-year post-transplant follow-up, while the long-term follow-up cohort contained 123 patients. Risk-adjusted identification of independent risk factors for compromised renal graft function (KDIGO stage ≥ IV) was performed using multivariable regression analysis adjusted for propensity score logits for parathyroidectomy before versus after renal transplantation. Intra-individual matched-pairs analyses were used to identify significant effects of post-transplant parathyroidectomy on graft function as assessed by estimated glomerular filtration rate (eGFR) and paired t tests.

RESULTS

Donor kidney function KDIGO stage III (P = .030; OR = 5.191, 95% CI: 1.100-24.508), donor blood group 0 (P = .005; OR = 0.176, 95% CI: 0.048-0.642), and post-transplant parathyroidectomy (P = .032; OR = 17.849, 95% CI: 1.086-293.268) were revealed as independent significant risk factors for compromised renal graft function in the short-term follow-up cohort using propensity score risk adjustment while post-transplant parathyroidectomy had no independent influence in the long-term follow-up cohort (P = .651). Parathyroidectomy after renal transplantation compromised graft function early after parathyroidectomy and at last follow-up in all post-transplant parathyroidectomy cases (P ≤ .004). Parathyroidectomy within the first post-transplant year was associated with compromised renal graft function until last follow-up (P = .004), while parathyroidectomy late post-transplant was not.

CONCLUSION

Parathyroidectomy should be conducted before transplantation or, if this is not possible, preferably after the first post-transplant year.

Cinacalcet for hypercalcaemic secondary hyperparathyroidism after renal transplantation: a multicentre, retrospective, 3-year study

AIMS

Our aim was to evaluate the long-term effect of cinacalcet in patients with hypercalcaemic secondary hyperparathyroidism (SHPT) after renal transplantation (RT) in order to expand real-world data in this population.

METHODS

We performed a multicentre, observational, retrospective study in 17 renal transplant units from Spain. We collected data from renal recipients with hypercalcaemic (calcium >10.2 mg/dL) SHPT (intact parathyroid hormone (iPTH) > 120 pg/mL) who initiated cinacalcet in the clinical practice.

RESULTS

We included 193 patients with a mean (standard deviation (SD)) age of 52 (12) years, 58% men. Cinacalcet treatment was initiated at a median of 20 months after RT (median dose 30 mg/day). Mean calcium levels decreased from a mean (SD) of 11.1 (0.6) at baseline to 10.1 (0.8) at 6 months (9.0% reduction, P < 0.0001). Median iPTH was reduced by 23.0% at 6 months (P = 0.0005) and mean phosphorus levels increased by 11.1% (P < 0.0001). The effects were maintained up to 3-years. No changes were observed in renal function or anticalcineurin drug levels. Only 4.1% of patients discontinued cinacalcet due to intolerance and 1.0% due to lack of efficacy.

CONCLUSIONS

In renal transplant patients with hypercalcaemic SHPT, cinacalcet controlled serum calcium, iPTH and phosphorus levels up to 3 years. Tolerability was good.

Recovery versus persistence of disordered mineral metabolism in kidney transplant recipients

In patients with end-stage renal disease, successful renal transplantation improves the quality of life and increases survival, as compared with long-term dialysis treatment. Although it long has been believed that successful kidney transplantation to a large extent solves the problem of chronic kidney disease-mineral and bone disorders (CKD-MBD), increasing evidence indicates that it only changes the phenotype of CKD-MBD. Posttransplant CKD-MBD reflects the effects of immunosuppression, previous CKD-MBD persisting after transplantation, and de novo CKD-MBD. A major and often-underestimated problem after successful renal transplantation is persistent hyperparathyroidism. Besides contributing to posttransplant hypercalcemia and hypophosphatemia, persistent hyperparathyroidism may be involved in the pathogenesis of allograft dysfunction (nephrocalcinosis), progression of vascular calcification, and bone disease (uncoupling of bone formation and bone resorption and bone mineral density loss) in renal transplant recipients. Similar to nontransplanted patients, CKD-MBD has a detrimental impact on (cardiovascular) mortality and morbidity. Additional studies urgently are needed to get more insights into the pathophysiology of posttransplant CKD-MBD. These new insights will allow for a more targeted and causal therapeutic approach.

Pain syndrome with stress fractures in transplanted patients treated with calcineurin inhibitors

Bone disease remains a major cause of morbidity after renal transplantation. Post-transplant osseous complications include osteoporosis and osteonecrosis, both historically associated with glucocorticoids, and a newer syndrome of bone pain associated with calcineurin inhibitors. Calcineurin inhibitor-induced pain syndrome (CIPS) is a reversible etiology of lower extremity bone pain and bone marrow edema reported in patients receiving cyclosporine or tacrolimus after solid organ or bone marrow transplantation. While the syndrome’s pathophysiology is unclear, bone insufficiency and epiphyseal impaction may play a role. We review the literature on this increasingly important post-transplant entity and describe a case illustrating the syndrome’s key features.

Clinical impact of hypercalcemia in kidney transplant

Hypercalcemia (HC) has been variably reported in kidney transplanted (KTx) recipients (5–15%). Calcium levels peak around the 3rd month after KTx and thereafter slightly reduce and stabilize. Though many factors have been claimed to induce HC after KTx, the persistence of posttransplant hyperparathyroidism (PT-HPT) of moderate-severe degree is universally considered the first causal factor. Though not proven, there are experimental and clinical suggestions that HC can adversely affect either the graft (nephrocalcinosis) and other organs or systems (vascular calcifications, erythrocytosis, pancreatitis, etc.). However, there is no conclusive evidence that correction of serum calcium levels might avoid the occurrence of these claimed clinical effects of HC. The best way to reduce the occurrence of HC after KTx is to treat as best we can the secondary hyperparathyroidism (SHP) during the uraemic stages. The indication to Parathyroidectomy (PTX), either before or after KTx, in order to prevent or to treat, respectively, HC after KTx, is still a matter of debate which has been revived by the availability of the calcimimetic cinacalcet for the treatment of PT-HPT. However, we still need to better clarify many points as regards the potential adverse effects related to either PTX or cinacalcet use in this clinical set, and we are waiting for the results of future randomized controlled trials to achieve some more definite conclusions on this topic.